Is it valid to use $ for variable name in JavaScript?

Question

Just wondering if it is valid to use $ in front of variable name in JavaScript (like PHP).

So can I do something like this:

var $x = 1; // Is this valid with the $ in front?
var y = 2; // This is valid JavaScript

I have tested a little and it seems to work, but want to make sure it is valid and will work across all browsers before I do it.

If you're writing new code, consider `const`/`let` rather than `var`. Their scope is much more clear/less quirky. — Brad, Jun 14 '20 at 04:03
Yes, it doesn't matter. This is an example you can refer: https://stackoverflow.com/q/43083577/1550476. — Thanh Nguyen, Jun 14 '20 at 04:03
Sure, check official docs: https://www.ecma-international.org/ecma-262/10.0/index.html#sec-names-and-keywords — Fabrizio Valencia, Jun 14 '20 at 04:09

score 2 · Answer 1 · answered Jun 14 '20 at 04:02

2

Javascript variable names can begin with a letter, $ or _ . As long as you dont start your variable name with a number, your good to go.

answered Jun 14 '20 at 04:02

DpK

100
4

score 2 · Answer 2 · answered Jun 14 '20 at 04:02

Valid, yes, but a code style not usually used unless it has meaning.

I've seen some folks use $someVar to indicate a jQuery-decorated element, for example. (Because, jQuery by default uses $ for its name.)

I would not recommend using it unless you have a specific reason, and are consistent in your codebase.

Flux · Accepted Answer · 2020-06-14T04:25:41.430

Yes, it has always been valid since the first edition of the ECMAScript language specification.

According to the 10th edition of the ECMAScript language specification published in 2019 (see: ECMAScript Language: Lexical Grammar - Names and Keywords), the grammar for variable names is:

IdentifierName::
  IdentifierStart
  IdentifierName IdentifierPart

IdentifierStart::
  UnicodeIDStart
  $
  _
  \ UnicodeEscapeSequence

IdentifierPart::
  UnicodeIDContinue
  $
  \ UnicodeEscapeSequence
  <ZWNJ>
  <ZWJ>

...

As you can see, it is valid to have $ anywhere in the variable name.

This has always been the case since the first edition of ECMAScript standard published in 1997. Section 4.5 Identifiers from the first edition says:

An identifier is a character sequence of unlimited length, where each character in the sequence must be a letter, a decimal digit, an underscore (_) character, or a dollar sign ($) character, and the first character may not be a decimal digit.

score 1 · Answer 4 · answered Jun 14 '20 at 04:06

1

Yes, Javascript accepts $ and _ as variable names. It works and it is valid in any browser.Check it here

answered Jun 14 '20 at 04:06

Sandren Troy Milante

53
1
10

Is it valid to use $ for variable name in JavaScript?

4 Answers4